Fragrance compound

{{short description|Chemical compound that has a smell or odor}} {{Redirect-several|dab=off|Fragrance (disambiguation)|Fragrant, Kentucky|The Odorants}} {{distinguish|Aromatic compound}} {{Use American English|date=March 2021}} {{Use mdy dates|date=March 2021}} [[File:Grapefruit mercaptan.svg|thumb|"Grapefruit mercaptan" can be detected by humans at the ppt level.<ref>{{cite journal|author1=Buettner A. |author2=Schieberle P. |title=Characterization of the Most Odor-Active Volatiles in Fresh, Hand-Squeezed Juice of Grapefruit (Citrus paradisi Macfayden)|journal= J. Agric. Food Chem.|volume= 47|issue= 12|pages= 5189–5193|year= 1999|doi=10.1021/jf990071l|pmid=10606593 |bibcode=1999JAFC...47.5189B }}</ref>|110px ]] A '''fragrance compound''' (or fragrance) is a chemical compound with a pleasant odor. Fragrances affect only the sense of smell, whereas flavors can affect both the sense of taste and smell. Fragrances are often mixtures of individual fragrance compounds. Although many fragrances are derived from natural sources, many are synthetic. Fragrances are widely used in cosmetics and are the basis for a large industry.<ref name=Ullmann>{{cite book|last1=Panten |first1=Johannes |last2=Surburg |first2=Horst |title=Ullmann's Encyclopedia of Industrial Chemistry |chapter=Flavors and Fragrances, 1. General Aspects |date=2015 |pages=1–9 |doi=10.1002/14356007.a11_141.pub2 |isbn=978-3-527-30673-2 }}</ref>

==Related odiferous compounds== Stench compounds have unpleasant odors. Some are used as odorizer or an odorant usually have an intense odor, which may be pleasant or not. They are sometimes used to confer a detectable odor to an odorless substance, like propane, natural gas, or hydrogen, as a safety measure.<ref>{{Cite journal |last1=Mouli-Castillo |first1=Julien |last2=Bartlett |first2=Sam |last3=Murugan |first3=Arul |last4=Badham |first4=Pete |last5=Wrynne |first5=Aidan |last6=Haszeldine |first6=Stuart |last7=Wheeldon |first7=Mark |last8=McIntosh |first8=Angus |date=2020-04-14 |title=Olfactory appraisal of odorants for 100% hydrogen networks |url=https://www.sciencedirect.com/science/article/pii/S0360319920306595 |journal=International Journal of Hydrogen Energy |volume=45 |issue=20 |pages=11875–11884 |doi=10.1016/j.ijhydene.2020.02.095 |bibcode=2020IJHE...4511875M |issn=0360-3199|url-access=subscription }}</ref>

==Occurrence== For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. Generally, fragrance compounds have molecular weights of less than 310.<ref>{{cite journal |last1=Rothe |first1=M |last2=Specht |first2=M |title=[Notes about molecular weights of aroma compounds] |journal=Nahrung |date=1976 |volume=20 |issue=3 |pages=281–6 |doi=10.1002/food.19760200308 |pmid=958345 }}</ref>

Fragrance compounds are found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form during the ripening of fruits and other crops.<ref name="haug">{{cite journal | last1=Haugeneder | first1=Annika | last2=Trinkl | first2=Johanna | last3=Härtl | first3=Katja | last4=Hoffmann | first4=Thomas | last5=Allwood | first5=James William | last6=Schwab | first6=Wilfried | title=Answering biological questions by analysis of the strawberry metabolome | journal=Metabolomics| volume=14 | issue=11 | date=2018-10-26 | issn=1573-3882 | pmid=30830391 | pmc=6394451 | doi=10.1007/s11306-018-1441-x | page=145}}</ref> Wines have more than 100 aromas that form as byproducts of fermentation.<ref name="ilc">{{cite journal | last1=Ilc | first1=Tina | last2=Werck-Reichhart | first2=Danièle | last3=Navrot | first3=Nicolas | title=Meta-analysis of the core aroma components of grape and wine aroma | journal=Frontiers in Plant Science| volume=7 | date=2016-09-30 | page=1472 | issn=1664-462X | pmid=27746799 | pmc=5042961 | doi=10.3389/fpls.2016.01472| doi-access=free | bibcode=2016FrPS....7.1472I }}</ref> Also, many of the aroma compounds play a significant role in the production of compounds used in the food service industry to flavor, improve, and generally increase the appeal of their products.<ref name=Ullmann/>

==History, biochemistry, economics== thumb|Fragrance bottles The technology of fragrances came with the invention of distillation, which allowed to be concentrated and sometimes even separated into individual components. The purification of cinnamaldehyde, the first single component fragrance, marked the beginning of the fragrance and flavor industries. Other single component fragrance compounds that were purified in the 19th century include benzaldehyde, methyl salicylate (oil of wintergreen), and vanillin. Somewhat in step with the synthetic dye industry, the fragrance and flavor industry was established. Many fragrance compounds were prepared synthetically. Spectroscopic methods coupled with various separation techniques allowed the identification of traces of aroma compounds (e.g. in wines, flower extracts, etc.).<ref name=Ullmann/> Tetramethyl acetyloctahydronaphthalenes have been described as "the most successful synthetic fragrance".<ref>{{cite journal |last1=Stepanyuk |first1=Alexey |last2=Kirschning |first2=Andreas |title=Synthetic terpenoids in the world of fragrances: Iso e Super®is the showcase |journal=Beilstein Journal of Organic Chemistry |date=2019 |volume=15 |pages=2590–2602 |doi=10.3762/bjoc.15.252 |pmid=31728173 |pmc=6839564 }}</ref>

The invention of gas chromatography was very important to the development of fragrances.<ref>{{cite journal|author1=Lehmann D. |author2=Dietrich A. |author3=Hener U. |author4=Mosandl A. |title=Stereoisomeric flavor compounds. LXX: 1-''p''-menthene-8-thiol: separation and sensory evaluation of the enantiomers by enantioselective gas chromatography-olfactometry|journal=Phytochemical Analysis|volume=6|issue= 5|pages=255–257|year= 1994 | doi = 10.1002/pca.2800060506}}</ref> Gas chromatography-olfactometry sometimes involving a human operator sniffing the GC effluent is particularly relevant to the analysis of fragrances.<ref>{{cite journal |last1=Brattoli |first1=M |last2=Cisternino |first2=E |last3=Dambruoso |first3=PR |last4=de Gennaro |first4=G |last5=Giungato |first5=P |last6=Mazzone |first6=A |last7=Palmisani |first7=J |last8=Tutino |first8=M |title=Gas chromatography analysis with olfactometric detection (GC-O) as a useful methodology for chemical characterization of odorous compounds. |journal=Sensors (Basel, Switzerland) |date=5 December 2013 |volume=13 |issue=12 |pages=16759–800 |doi=10.3390/s131216759 |pmid=24316571 |pmc=3892869|bibcode=2013Senso..1316759B |doi-access=free }}</ref> GC-O and related techniques have also been developed to characterize individual enantiomers of chiral aromatic compounds.

Studies on synthetic musk reveal that the odors of some compounds are noticeably affected by deuteration.<ref>{{cite journal | last1 = Gane | first1 = S | last2 = Georganakis | first2 = D | last3 = Maniati | first3 = K | last4 = Vamvakias | first4 = M | last5 = Ragoussis | first5 = N | last6 = Skoulakis | first6 = EMC | last7 = Turin | first7 = L | year = 2013 | title = Molecular-vibration-sensing component in human olfaction | journal = PLOS ONE | volume = 8 | issue = 1| article-number = e55780 | doi = 10.1371/journal.pone.0055780 | pmid=23372854 | pmc=3555824| bibcode = 2013PLoSO...855780G | doi-access = free }}</ref>

Various fragrant fruits are commercially cultivated to have appealing or intensified aromas.<ref name="ulrich">{{cite journal | last1=Ulrich | first1=Detlef | last2=Kecke | first2=Steffen | last3=Olbricht | first3=Klaus | title=What do we know about the chemistry of strawberry aroma? | journal=Journal of Agricultural and Food Chemistry | volume=66 | issue=13 | date=2018-03-13 | issn=0021-8561 | pmid=29533612 | doi=10.1021/acs.jafc.8b01115 | pages=3291–3301 | bibcode=2018JAFC...66.3291U }}</ref>

== Fragrance compounds classified by chemical structure == {{Main|List of fragrance compounds}} In 2010, the International Fragrance Association published a list of 3,059 chemicals used in 2011 based on a voluntary survey of its members, identifying about 90% of the world's production volume of fragrances.<ref name="Weinberg">{{cite journal |last1=Weinberg |first1=JL |last2=Flattery |first2=J |last3=Harrison |first3=R |title=Fragrances and work-related asthma-California surveillance data, 1993-2012. |journal=The Journal of Asthma |date=December 2017 |volume=54 |issue=10 |pages=1041–1050 |doi=10.1080/02770903.2017.1299755 |pmid=28332885 |issn=0277-0903}}</ref><ref>{{cite web| url=http://www.ifraorg.org/en-us/ingredients#.VH-EkXsdXYg|title=IFRA Survey:Transparency List |publisher=IFRA| access-date=December 3, 2014|url-status=dead}}</ref>

=== Esters ===

{| class="wikitable" style="font-size: 110%" ! Compound name ! Fragrance ! Natural occurrence ! Chemical structure |-align=center | Geranyl acetate | Fruity, Floral | Rose | x40px|center|class=skin-invert-image |-align=center | Methyl formate | Ethereal | synthetic | x40px|center|class=skin-invert-image |-align=center | Methyl acetate | Sweet, nail polish Solvent | synthetic | x40px|center|class=skin-invert-image |-align=center | Fructone | fruity, apple-like | synthetic |100px|center|class=skin-invert-image |-align=center |Ethyl methylphenylglycidate |Strawberry |synthetic | 100px|center|class=skin-invert-image |-align=center | Methyl propionate | Sweet, fruity, rum-like | | x40px|center|class=skin-invert-image |-align=center | Methyl butyrate | Fruity | Apple Pineapple | x40px|center|class=skin-invert-image |-align=center | Ethyl acetate | Sweet, solvent | Wine | x40px|center|class=skin-invert-image |-align=center | Ethyl butyrate | Fruity | Orange, Pineapple | x40px|center|class=skin-invert-image |-align=center | Isoamyl acetate | Fruity, Banana, Pear | | Banana plant | x40px|center|class=skin-invert-image |-align=center | Pentyl butyrate | Fruity | Pear Apricot | x40px|center|class=skin-invert-image |-align=center | Pentyl pentanoate | Fruity | Apple | x40px|center|class=skin-invert-image |-align=center | Octyl acetate | Fruity | Orange | x40px|center|class=skin-invert-image |-align=center | Benzyl acetate | Fruity, Strawberry | | Strawberries | x40px|center|class=skin-invert-image |-align=center | Methyl anthranilate | Fruity | Grape | x50px|center|class=skin-invert-image |-align=center | Methyl salicylate | Minty, root beer | Wintergreen | x50px|center|class=skin-invert-image |-align=center | Hexyl acetate | Floral, Fruity |Apple, Plum | x50px|center|class=skin-invert-image |}

=== Linear terpenes === {| class="wikitable" style="font-size: 110%" ! Compound name ! Fragrance ! Natural occurrence ! Chemical structure |-align=center | Myrcene | Woody, complex | Verbena, Bay leaf | 140px|center|class=skin-invert-image |-align=center | Geraniol | Rose, flowery | Geranium, Lemon | center|140px|class=skin-invert-image |-align=center | Nerol | Sweet rose, flowery | Neroli, Lemongrass | 140px|center|class=skin-invert-image |-align=center | Citral, lemonal Geranial, neral | Lemon | Lemon myrtle, Lemongrass | 140px|center|class=skin-invert-image |-align=center | Citronellal | Lemon | Lemongrass | 140px|center|class=skin-invert-image |-align=center | Citronellol | Lemon | Lemongrass, rose Pelargonium | 140px|center|class=skin-invert-image |-align=center | Linalool | Floral, sweet Woody | Coriander, Sweet basil, Lavender, Honeysuckle | 140px|center|class=skin-invert-image |-align=center | Nerolidol | Woody, fresh bark | Neroli, ginger Jasmine | 140px|center|class=skin-invert-image |-align=center | Ocimene | Fruity, Floral | Mango, Curcuma amada | 140px|center|class=skin-invert-image |}

=== Cyclic terpenes === {| class="wikitable" style="font-size: 110%" ! Compound name ! Fragrance ! Natural occurrence ! Chemical structure |-align=center | Limonene | Orange | Orange, lemon | x60px|center|class=skin-invert-image |-align=center | Camphor | Camphor | Camphor laurel | x60px|center|class=skin-invert-image |-align=center | Menthol | Menthol | Mentha | x60px|center|class=skin-invert-image |-align=center | Carvone1 | Caraway or Spearmint | Caraway, dill, spearmint | x60px|center|class=skin-invert-image |-align=center | Terpineol | Lilac | Lilac, cajuput | x60px|center|class=skin-invert-image |-align=center | alpha-Ionone | Violet, woody | Violet | x60px|center|class=skin-invert-image |-align=center | Thujone | Minty | Wormwood, lilac, juniper | x60px|center|class=skin-invert-image |-align=center | Eucalyptol | Eucalyptus | Eucalyptus | x60px|center|class=skin-invert-image |-align=center | Jasmone | spicy, fruity, floral in dilution | Jasmine, Honeysuckle | x60px|center|class=skin-invert-image |}

Note: Carvone, depending on its chirality, offers two different smells.

=== Aromatic === {| class="wikitable" style="font-size: 110%" ! Compound name ! Fragrance ! Natural occurrence ! Chemical structure |-align=center | Benzaldehyde | Almond | Bitter almond | x60px|center|class=skin-invert-image |-align=center | Eugenol | Clove | Clove | x60px|center|class=skin-invert-image |-align=center | Cinnamaldehyde | Cinnamon | Cassia Cinnamon | x60px|center|class=skin-invert-image |-align=center | Ethyl maltol | Cooked fruit Caramelized sugar | | x60px|center|class=skin-invert-image |-align=center | Vanillin | Vanilla | Vanilla | x60px|center|class=skin-invert-image |-align=center | Anisole | Anise | Anise | x60px|center|class=skin-invert-image |-align=center | Anethole | Anise | Anise Sweet basil | x60px|center|class=skin-invert-image |-align=center | Estragole | Tarragon | Tarragon | x60px|center|class=skin-invert-image |-align=center | Thymol | Thyme | Thyme | x60px|center|class=skin-invert-image |}

== Other aroma compounds ==

=== Alcohols ===

* Furaneol (strawberry) * 1-Hexanol (herbaceous, woody) * ''cis''-3-Hexen-1-ol (fresh cut grass)

=== Aldehydes === High concentrations of aldehydes tend to be very pungent and overwhelming, but low concentrations can evoke a wide range of aromas. * Acetaldehyde (ethereal) * Hexanal (green, grassy) * ''cis''-3-Hexenal (green tomatoes) * Furfural (burnt oats) * Hexyl cinnamaldehyde * Isovaleraldehyde – nutty, fruity, cocoa-like * Anisic aldehyde – floral, sweet, hawthorn. It is a crucial component of chocolate, vanilla, strawberry, raspberry, apricot, and others. * Cuminaldehyde – Spicy, cumin-like, green

=== Ketones === * Dihydrojasmone (fruity woody floral) * Oct-1-en-3-one (blood, metallic, mushroom-like)<ref name="metallic">{{cite journal | author= Glindemann, D. | author2= Dietrich, A. | author3= Staerk, H. | author4= Kuschk, P. | title = The Two Odors of Iron when Touched or Pickled: (Skin) Carbonyl Compounds and Organophosphines | journal = Angewandte Chemie International Edition | year = 2005 | volume = 45 | issue = 42 | pages = 7006–7009 | doi = 10.1002/anie.200602100 | pmid= 17009284| doi-access = }} </ref> * 2-Acetyl-1-pyrroline (fresh bread, jasmine rice) * 6-Acetyl-2,3,4,5-tetrahydropyridine (fresh bread, tortillas, popcorn) * Diacetyl (butter flavor) * Acetoin (butter flavor)

===Lactones=== * gamma-Decalactone intense peach flavor * gamma-Nonalactone coconut odor, popular in suntan lotions * delta-Octalactone creamy note * Jasmine lactone powerful fatty-fruity peach and apricot * Massoia lactone powerful creamy coconut * Wine lactone sweet coconut odor * Sotolon (maple syrup, curry, fenugreek)

==Detection and interpretation== {{Main|Olfaction}}

Fragrances are detected by the nose when the movement of inspired air contacts olfactory sensory neurons, which in humans, number between 6 and 10 million over a surface area of {{cvt|2.5|cm2}} of olfactory epithelium.<ref name="helwany">{{cite web |vauthors=Helwany M, Bordon B |title=Neuroanatomy, Cranial Nerve 1 (Olfactory) |url=https://www.ncbi.nlm.nih.gov/books/NBK556051/ |publisher=StatPearls, US National Library of Medicine |access-date=31 December 2025 |date=14 August 2023 |pmid=32310511 }}</ref> Fragrance signals are conveyed from the epithelium to the olfactory nerves, and then to the olfactory bulbs, which relay neural impulses about fragrance properties into the primary olfactory cortex of the brain.<ref name=helwany/> In the olfactory cortex, fragrance characteristics are integrated to evaluate the safety and appeal of compounds to be ingested, and to recognize environmental and social factors associated by memory with the fragrance.<ref name=helwany/><ref name="branigan">{{cite web |vauthors=Branigan B, Tadi P |title=Physiology, Olfactory |url=https://www.ncbi.nlm.nih.gov/books/NBK542239/ |publisher=StatPearls, US National Library of Medicine |access-date=31 December 2025 |date=1 May 2023 |pmid=31194396 }}</ref>

== Safety and regulation == [[File:Epikutanni-test.jpg|thumb|right|Patch test]]

In 2005–06, fragrance mix was the third-most-prevalent allergen in patch tests (11.5%).<ref name="autogenerated2005">{{Cite journal |last1=Zug |first1=Kathryn A. |last2=Warshaw |first2=Erin M. |last3=Fowler |first3=Joseph F. |last4=Maibach |first4=Howard I. |last5=Belsito |first5=Donald L. |last6=Pratt |first6=Melanie D. |last7=Sasseville |first7=Denis |last8=Storrs |first8=Frances J. |last9=Taylor |first9=James S. |last10=Mathias |first10=C. G. Toby |last11=Deleo |first11=Vincent A. |last12=Rietschel |first12=Robert L. |last13=Marks |first13=James|display-authors=3 |date=2009 |title=Patch-test results of the North American Contact Dermatitis Group 2005-2006 |journal=Dermatitis: Contact, Atopic, Occupational, Drug |volume=20 |issue=3 |pages=149–160 |doi=10.2310/6620.2009.08097 |issn=2162-5220 |pmid=19470301}}</ref> 'Fragrance' was voted Allergen of the Year in 2007 by the American Contact Dermatitis Society. An academic study in the United States published in 2016 has shown that "34.7 % of the population reported health problems, such as migraine headaches and respiratory difficulties, when exposed to fragranced products".<ref>{{cite journal |last1=Steinemann |first1=A |title=Fragranced consumer products: exposures and effects from emissions. |journal=Air Quality, Atmosphere, & Health |date=2016 |volume=9 |issue=8 |pages=861–866 |doi=10.1007/s11869-016-0442-z |pmid=27867426 |bibcode=2016AQAH....9..861S |author-link=Anne C. Steinemann|pmc=5093181 |hdl=11343/121889 |hdl-access=free }}</ref>

The composition of fragrances is usually not disclosed in the label of the products, hiding the actual chemicals of the formula, which raises concerns among some consumers.<ref>{{cite journal |last1=Steinemann |first1=AC |last2=MacGregor |first2=IC |last3=Gordon |first3=SM |last4=Gallagher |first4=LG |last5=Davis |first5=AL |last6=Ribeiro |first6=DS |last7=Wallace |first7=LA|display-authors=3 |title=Fragranced consumer products: Chemicals emitted, ingredients unlisted |journal=Environmental Impact Assessment Review |date=1 April 2011 |volume=31 |issue=3 |pages=328–333 |doi=10.1016/j.eiar.2010.08.002 |bibcode=2011EIARv..31..328S |url=https://doi.org/10.1016/j.eiar.2010.08.002 |issn=0195-9255|url-access=subscription }}</ref> In the United States, this is because the law regulating cosmetics protects trade secrets.<ref name="FDA fragranaces">{{Cite web |date= August 22, 2024|title=Fragrances in Cosmetics {{!}} FDA |url=https://www.fda.gov/cosmetics/cosmetic-ingredients/fragrances-cosmetics |website=Food and Drug Administration}}</ref>

In the United States, fragrances are regulated by the Food and Drug Administration if present in cosmetics or drugs, by the Consumer Product Safety Commission if present in consumer products.<ref name="FDA fragranaces" /> No pre-market approval is required, except for drugs. Fragrances are also generally regulated by the Toxic Substances Control Act of 1976 that "grandfathered" existing chemicals without further review or testing and put the burden of proof that a new substance is not safe on the EPA. The EPA, however, does not conduct independent safety testing but relies on data provided by the manufacturer.<ref>{{cite book |last1=Fitzgerald |first1=Randall |title=The hundred-year lie: how food and medicine are destroying your health |date=2006 |publisher=Dutton |location=New York |isbn=0-525-94951-8 |url=https://archive.org/details/hundredyearlieho00fitz/page/23 |page=23}}</ref>

A 2019 study of the top-selling skin moisturizers found 45% of those marketed as "fragrance-free" contained fragrance.<ref>{{cite web|url=https://www.npr.org/sections/health-shots/2017/10/02/554365324/hypoallergenic-and-fragrance-free-moisturizer-claims-are-often-false |title='Hypoallergenic' And 'Fragrance-Free' Moisturizer Claims Are Often False|author-first=Patti |author-last=Neighmond|publisher=NPR|date=2 October 2017}}</ref>

== See also == {{Portal|Chemistry}} {{div col|colwidth=18em}} * Aroma of wine * Eau de toilette * ''Flavour and Fragrance Journal'' * ''Fragrances of the World'' * Foodpairing * Odor * Odor detection threshold * Odorizer, a device for adding an odorant to gas flowing through a pipe * Olfaction * Olfactory receptor * Olfactory system * Pheromone * ''The Hundred Year Lie'' * Vabbing {{end div col}}

== References == <references/>

{{DEFAULTSORT:Aroma Compound}} Category:Organic chemistry Category:Olfaction Category:Flavors *